Polyfurcate azonitriles



Patented Feb. 26, 1952 a 2,586,995

UNITED STATES PATENT OFFICE.

POLYFURCATE AZONITRILES James A. Robertson, Wilmington, Del., assignor to E. I. du Pont de Nemours & Cmpany, Wilmington, DeL, a corporation of Delaware No Drawing. Application January 15, 1948, Serial No. 2,552

Claims. (01. 260-192) 1 2 This invention relates to new azo compounds of The azine boiling at 95-105" C. at 8 mm. pressure particular utility in addition polymerization. was obtained. The azine has the-formula The polymerization of polymerizable compounds containing an ethylenic double bond has -E(CH3)2C(QC2H5)CHPC(C;-I3) N ]2 been initiated by a wide variety of compounds. 5 y The azine was mixed withabout 40 parts 01 Peroxides have been widely used for this purpose. liquid hydrogen cyanide containing less than 5% Certain azo compounds have been found useful water and allowed to stand 48 hours at about for this purpose. Others have been found to be room temperature. Excess hydro en cy nide Wa without initiatory activity. evaporated under reduced pressure and the re- This invention has as an object the preparation :0 sidual hydrazonitrile was stirred With about 25 of new azo compounds. A further object is the parts of ethanol, 75 partswater and 25 parts conprovision of new catalysts or initiators for the centrated hydrochloric acid, cooled to 0-10 C. and

' addition polymerization of polymerizable comchlorine gas introduced into themixture until an pounds containing an ethylenic double bond. excess was present. The azonitrile was collected Other objects will appear hereinafter. on a filter and dissolved in ether. The ether so- These objects are accomplished by the invenlution was dried over anhydrous magnesium sultion of acyclic azo compounds in which the acyclic fate and the azonitrile precipitated by cooling the azo, -N=N, group is bonded to different, i; e., ether solution with solid carbon dioxide. The distinct, i. e., discrete, tertiary carbons whose solid isomer of the azonitrile was obtained by filthree remaining valences are satisfied by (1) a tration while the liquid isomer remained in solunitrile group, (2) a methyl group and (3) a methtion. The solid isomer melted at 85-87 C. The ylene group further bonded to a hydrogen free total yield of azonitrile was 64% based on the carbon. The preferred azo compounds are repreketone. The analysis of the azonitrile was: Calsented by the general formula culated for R ON ON R [(CH3)2-C(OCzH5)CH2-C(CH3) (cm-41:12 E J L c, 64.3; H; 10.1; N, 16.7. Found: c, 64.2; 11,-9.7;

H H N, 17.3. v

EXAMPLE II where R and R are lower alkyl radicals 1-4 car- Preparation of alpha,alpha-azobis(alpha, ambon alkyls) and A is a radical attached to the ma-dimethyl-gamma-methoxyvaleronitrile) gamma carbon by a non-metallic element of CH3 CH3 CH3 atomic number of at least 6, e. g., oxygen, carbon,

The following examples in which parts are by H: N N a weight are illustrative of the invention. The general procedure of Example I was repeated with methyl beta-methoxyisobutyl ketone EXAMPLE I (obtained by the process of U. s. Patent 1,823,704) as the ketone. There was obtained a 48% yield of alpha,alpha'-azobis(alpha,gammadimethyl-gamma-methoxyvaleronitrile) as two isomers which after separation melted at 58 and 107 C. The analysis was: Calculated for Preparation of alpha, alpha azobz'smlpha, 40

gamma-dimethyl-gamma-etho:cyvaleronitrile In a container fitted with a reflux condenser and stirrer were placed 20 parts of methyl betaethtorxyisoguglmtone;obtained accordin to the C1eHzsN2O4' me 0d 0 0 man, Am. Chem. Soc. 49, 432 Q (1927)) and.3.5 parts of hydrazine hydrate. The g 3' 7 mole ratio of hydrazine to ketone was one to two. EXAMPLE m After refluxing for six hours, the organic productwas extracted with ether and the-extract dried Preparation of alpha,alpha'-azobis(alpha,gamover anhydrous magnesium sulfate and distilled. ma-dimethyl-gamma-n-butoxyvaleronitrile) The general procedure of Example I was repeated with methyl beta-n-butbxyisobutyl ketone (obtained by the Hofiman procedure) as the ketone. There was obtained an 11% yieldof alpha,alpha azobis(alpha,gamma dimethylgamma-n-butoxyvaleronitrile) melting at 69-71" C. The analysis was: Calculated for C27H40N4O2: C, 67.3; 11,102; N, 14.3. Found: C, 66.4; 11,103; N, 13.9.

EXAMPLE IV Preparation of alphanlpha'-a2obis(alpha,gamma,gamma-trimethylvaleronitrile) The general procedure of Example I was .repeated with methyl neopentyl ketone (obtained by the process of McCubben and Adkins, J. Am. Che SOC- 2547 (1930)) as the ketone. There was obtained a 29% yield of alphaalpha azobis (alpha,gamma,gamma-trimethylvaleronitrile) as two isomers which after separation melted at 65 and 102-103 C.. The analysis was: Calculated 101' can-2am: C, 69.6: H, 10.1; N, 20.3.

Found: C, 69.7; H. 10.3; N, "20.5.

EXAMPLE V Preparation of aZpha,aZ pha'-azobis(alpha,gam-

ma-dimethyZ-gamma-phenylva;leronitrile) $113 CH3 CH3 CH3 CEH5-(JCHT(IJN=NJ -CH2-(1I-CBES n: N tn CH3 The general procedure of Exam le I was repeated with methyl beta-phenylisobutylketone (obtained by the process of Hoffman, J. Am. Chem. Soc. 51, 2543 (1929 as the ketone. There was obtained a 26% yield of alpha,alpha'-azobis(alpha gamma-dimethyl-gamma phenylvaleroni-trile) melting at 75-76 C. The analysis was: Calculated for CzsHszNir C, 78.0; H, 8.0.; N, 14.0. Found: C, 77.5; H, 8.1; N, 14.0.

EXAMPLE VI Preparation of alphmalphw-azobis(alphagamma-dimethyl-gamma-carboccyvaleronitrile) on. on. on. em Hooo-t-o m-o-N=N-o-oH2- 3co OH on: CN ON om To a solution of 24 parts of methyl beta-carboxyisobutyl ketone (prepared by the process of Lapworth. J. Am. Chem. Soc. 85, 1218 (1904)) in 100 parts of water containing 6.9 parts of sodium hydroxide was added 4 parts of hydrazine hydrate. After standing hours at room temperature, 31 parts of hydrogen cyanide was added. This mixture was maintained at 25 C. for 16 hours and poured into dilute hydrochloric acid after removal of excess hydrogen cyanide and hydrochloric acid, the solid product was filtered and crystallized from aqueous ethanol. The acid hydrazonitrile thus obtained melted at 175 C. A total of 4 parts of the hydrazonitrile was slurried in a solution of 50 parts of water and 15 parts concentrated hydrochloric acid. Chlorine was passed in until an excess was present. The solid product obtained was filtered and crystallized from ethanol. There was obtained a 25% yield based on the ketone of alpha,alpha-azo- 'bis('alpha,gamma dimethyl-gamma-carboxyvaleronitrile) melting at 140 C. The analysis was:

4 Calculated for C16H24N4041 C, 57.1; H, 7.11. Found: C, 57.3; H, 7.3.

EXAMPLE VII Polymerization of acrybo nz'trile' [:N-C (CH3) (CN) CH2C(A) (CH3)2]2 These catalysts are present in substantially equimclar amounts.

TABLE I Catalyst (parts by weight) Cataly t A Pet icent When the above procedure wasrepeated-except that the polymerization time was increased to 5 /2 hours and the catalyst was that of Example V (i. e., .A in the above formula was C6H5), the per cent of conversion of the monomor to polymer was 85. The per cent conversion of the control (A in the above formula was-1H) at 5% hours was 57 In a similar .manner, the catalyst of Example VI (1. e., A=COOH)., was effeotiveasa polymerization catalyst at 60 C.

The activity of the ,azo catalysts of the above general formula which have no hydrogen ion the gamma carbon is shown by reference to the .low conversion-,efiected by the last compound in Table I (A=H, i. e., alpha,alpha'-azobis.(alpha,gammadimethylvaleronitrile)), which has hydrogen on the gamma carbons. Example VIII further compares the activity of the latter compound with a compound coming under the scope of this invention.

EXAMPLE VIII Polymerization of methyl methacrylate Under the same conditions of temperature (38.9" C.), and catalyst concentration in the bulk polymerization of methyl methacrylate monomer containing 3% methyl methacrylate polymer and 0.007% methacrylic acid (using about 0.005% of catalyst), the polymerization time to obtain a completely polymerized sheet with alpha,alpha'- azobis(alpha,gamma dimethyl gamma methoxyvaleronitrile) was one-half that required for alpha,alpha' azobis(a1pha,gamma dimethylvaleronitrile) and one-fourth that required when benzoyl peroxide was employed (30 .hours') EXAMPLE IX Polymerization of vinyl chloride A series of pressure bottles were each charged with 40 parts vinyl chloride, 47 parts .cyclohexane and 0.5 mole per cent of are-catalyst. The bottles and contents were heated at 28 C. for 16 hours. The following table shows the amount of polymerization for different catalysts of the formula [=NC (CH3) (CN) CH2C(A) (CH3)2]2.

TABLE II Catalyst (parts by weight) Conversion catalyst A- Per cent EXAMPLE X Polymerization of ethylene A pressure reactor was charged with 80 parts of benzene and 0.1 part alpha,alpha azobis- (alpha,gamma dimethyl gamma methoxyvaleronitrile). After removal of oxygen, the reactor was charged with ethylene and heated to 50 C. During the reaction period (8 hours), the ethylene pressure was maintained at 800-900 atmospheres. After cooling and removal of excess ethylene, there was obtained 4 parts of polyethylene which had a tensile strength of 2930 p. s. i. at an elongation of 19%.

EXAMPLE XI Copolymerz'eation of dichlorodifluoroethylenes with vinyl chloride Two silver-lined pressure reactors of capacity of 400 parts of water were each charged with 225 parts of water, 1 part NBAPZO'I, 0.15 part alpha,- .alpha' azobis(alpha,gamma dimethyl-gammamethoxyvaleronitrile) 50 parts vinyl chloride and 10 parts dichlorodifiuoroethylene. The reactors and contents were heated at 40-50 C. for about 12-45 hours at 900 atmospheres pressure. When the dichlorodifiuoroethylene was 1,1-dich1oro-2,2- difiuoroethylene, there was obtained 43 parts of polymer which contained 11.2% fluorine. When the dichlorodifiuoroethylene was 1,2-dichloro-1,2- difiuoroethylene, there was obtained 40 parts of polymer which contained 14.3% fluorine.

EXAMPLE XII Polymerization of vinyl acetate A flask equipped with a stirrer was charged with 1100 parts of vinyl acetate, 275 parts of methanol and 4.5 parts of alpha,a1pha'-azobis- (alphagamma dimethyl gamma-methoxy-valeronitrile). The charge was stirred under a nitrogen atmosphere at 30 C. for 4% hours. There was obtained a 31% yield of polyvinyl acetate. Under the same conditions except that alpha,- alpha' azobisl'alphagamm dimethylvaleronitrile) was used as the catalyst, no polymer was obtained.

Addition polymerization (including copolymerization) of polymerizable compounds containing at least one ethylenic'double bond including polymerizab-le vinyl and vinylidene compounds, polymerizable hydrocarbons containing a vinyl group, etc. is catalyzed at relatively low temperatures with unusual speed by the azo compounds of this invention. Thus the azo compounds of this invention are useful as initiators in the polymerization and copolymerization of ethylene, tetrafluoroethylene, styrene, vinyl and vinylidene halides, e. g., vinyl fluoride, vinylidene chloride, vinyl esters, e. g. vinyl acetate, acrylyl and methacrylyl compounds, e. g., acrylonitrile, methacrylonitrile, and. methacrylamide, and compounds containing two or more isolated or conjugated ethylenic double bonds, e. g. the diacrylic acid esters of glycol and polyethylene glycols, tetraethylene glycol di- 6 methylacrylate, diallyl diglycolate, diallyl carbonate, diallyl phthalate, ethylene bis(a1lyl maleate), butadiene, chloroprene, styrene/maleic anhydride mixture, etc. These polymerizable vinylidene compounds, including polymerizable vinyl compounds, mostly are polymerizable unsaturated compounds having a CH2=C group, i. e. are

. monomeric unsaturated polymerizable compounds in which the unsaturation is due to one or a plurality of, i. c. more than one, terminal ethylenic group to which is attached a negative radical.

The new azo compounds of this invention may be prepared in the general manner described in Example I, i. e., reacting hydrazine with at least two moles of a ketone of the general formula wherein R and R are lower aliphatic radicals, preferably alkyl radicals of one to four carbons, e. g. CH3, ,CzHs, CsI-Iq and CH9, and A is a radical which is attached to the carbon of the ketone by a non-metallic element of atomic number of at least 6 and preferably 6 to 8. The radical A may be COOH, CH, C00 alkyl, aryl, alkyl, alkoxy, halogen, e. g., chlorine, hydroxyl, acetyl, amino substituted amines as diethylamino, sulfur as in a thiol.

The azine compound thus produced is reacted with excess hydrogen cyanide generally containing less than water to give the hydrazonitrile. The hydrazo compound obtained by this reaction is oxidized to the azo compound by such oxidizing agents as chlorine or bromine. The azo compounds thus obtained are represented by the formula where R, R, and A are as above. The preferred catalysts because of their great activity at'relatively low temperature, e. g. 20-50 C., are those of the formula where n is a cardinal number not more than 1, i. e., 0 or 1, and R is a monovalent hydrocarbon radical of one to six carbons. Of these the compounds where -0nR is an alkoxy radical of one to four carbons are particularly effective in polymerization.

In addition to the increased speed of polymerization obtained in the polymerization of compounds containing ethylenic unsaturation, these azo compounds are generally free from tendencies to discolor the polymer, to oxidize the polymer, to give cross-linking effects in the polymer, and to oxidize any added dyestuffs or pigments.

The azo compounds of this invention are useful as intermediates in the preparation of the corresponding dinitrile (i. e., by removal of the azo nitrogens) by decomposition by heat. Compounds of the general type represented by the general formula but which have the cyano group replaced by carbalkoxy, e. g., carbethoxy, or carbonamide can be prepared from the nitrile by treatment with alcoholic hydrogen chloride followed by hydrolysis with water to give the ester and treatment of the ester with ammonia or an appropriate hydrogen-bearing amine to give the 1 amide. The. carbalkoxy ands carbonamide groups are negative groups" neutral with respect to acidityand compounds having these groupsare also useful for polymerization of ethylenically unsaturated polymerizable compounds.

The foregoing detailed description has been given for clearness of. understanding only andno unnecessary limitations are to be. understood therefrom. The invention is not limited to the exact details shown: and. described for obvious modifications will occur to those skilledin the art.

What is claimed is: 1. An azonitrile of theformula CH3 CH3 Gm CH3 RO- -CH -N=N- Azure-B H3 N (BN H3 wherein R is an alkyl group of one to four carbons.

2. A lraolyfurcatev azonitrile of the formula where n. is a cardinal number not greater than 1 and R is a monovalenthydrocarbon radical of one to six carbons.

3. A1pha,a1pha' -azobis alpha,gamma-dimethylgamma-methoxyva1eronitrile) of the formula CH3 (EH3 CH3 CH3 CEuO-d-(JHEQAWN-o-Cm- -0cm H; N N CH:

4.. Alpha,alpha' azobis(alpha,gamma,gammatrimethylvaleronitrile) of the formula CH3 CH3 CH3 CH3 CH:(:JCHQAN=N- CHz- CH;

on; N (1N H:

5. An azonitrile of. the. formula wherein R is a monovalent hydrocarbon radical of one to six carbons.

JAMES A. ROBERTSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Dox, JACS, v. 47 (1925), p. 1471-1477, 7 pages. Hartman, Chem. Weekblad, v. 23 (1926), p. 77- 78, 2 pages. 

2. A POLYFURCATE AZONITRILE OF THE FORMULA 